Hello and welcome. Yes it's a good start the extender and batteries. I got a
gamesir g3s controller from incredible connection at r350 yesterday. (it was lying in the clearance goods ?). The
gamesir t1s I ordered is still in transit from alie xpress for the last 4 months so I already got refunded. The reason for the controller is that I can use it wired to my phone and hence no lag. The
tello is sometimes more about network management than flying so the less interference the better. If you want to do yourself a huge favor get the
tello fpv app by volatello. It is the best upgrade you can do. And with 3 batteries it is wise to get a multi charger so that you can charge them all at once. And a case is also essential to protect and store your drone. Enjoy